Power actuator



7, 1927 2 Sheets-Sheet l lNvENTOi n 7" ww ATTORNEY @et 1931. c. s. ERAGGET AL POWER ACTUATOR Original Filed' Nov'.

@et 6, 1931. v. C, 5 BRAGG ET AL LSZGA? POWER ACTUATOH original FiledNov. 7, 1927 2 sheets-sheet 2 Patented Oct. 6, 19.31 A

I UNITED STATES PATENTI OFFICE CALEB S. BRAGG AND VCTOR 'W'. OF LONGISLAND CITY, NEW YORK, AS-

SIGNORS` T0 BRAGG-KLL'ESRATH TION OF NEW YORK coRroRATIoN, or NEW YORK,N. Y., A CORPORA- v l P GWER ACTUATOR Application mea November '7,f1a7,serieiuo. 231,725. Renewed December a, 1930.

Our invention consists inthe novel features hereinafter described,reference being had to the accompanying drawings, which show severalembodiments of the invention, selected by us for purposes ofillustration, and the said invention is fully disclosed in the followingdescription and claims.

Our invention is an improvement in power actuators for use in connectionwith automotive vehiclesA and especially adapted for operating the brakemechanism thereof, and

it has for its object.v to provide means whereby the operator is enabledto determine by variations in the resistance to theoperator operatedpartfconnected with the valve mechanism for controlling ythe actuator,as' for example, by the variations in pressure against his foot, where apedal lever 1s em-l ployed to actuate the valve mechanism, how muchpressure the piston of theactuator 1s exerting on the brakes or other.part to be actuated. v 1

According to our present invention, varlaf tions in the differentialofzuid pressure on `the higher pressure valve-arid-lower pressure valveoperate to increase the initial resistance to the movement of theoperator vroperated ,part, as the higher pressure fiuidisadmitted to thec linder f the actuator, and pressure accumu ates therein, to effect apower stroke of the piston of the -actuator to apply the brakes,oractuatethe part connected w1th the piston.

Referring to the accompanying drawlngs, Fig. 1 is a diagrammatic viewillustrating an installation in an automotive vehicle, of a poweractuator connected with brake mech# anism for the vehicle and derivingits suction from the intake manifold of an internal combustion enginefor propelling the vehicle, and embodying our invention. i

Fig. 2 is an enlarged sectional view of the actuator shown in Fig. 1.

Fig. B is a still further enlarged sectional view of the valve mechanismof the actuator, showing the positions of the valves inl the normal orretracted position of the piston.

Fig. 4e is a view similar to Fig. 3, showing the position of the valveswhenino'ved to vided with a chamber, 11, or valve casing,

within the hub, and provided with a valve seat, 12, engaged by a valve,14, which in this instance is the higher pressure valve, and which ,whenseated, separates the outer portion, indicated at 11, which latterportion is atv all times in communication with the portionl of thecylinder in rearof the plston by means of ports or passages, 13.y

The valve, 14, is of considerable diameter, and is provided on its rearface with a cylindrical recess, 17 in which the other controlling valve,16, in this instance the suction or lower pressure valve, of mushroomshape, and having a sealing engagement with vthe ,cylindrical walls ofthe chamber or recess,

17, in this instance by means of an annular packing or gasket, 16". Theinterior of the chamber, 17, is provided with a seat, 19, en-

gaged by the valve, 16, when the latter` is in closed position, and thesaid valve is provided with a hollow stem, 20, communicating with thechamber, 17 by a passage, 21, independently of the valve seat andcommunicating also with the source of lower pressure, in this instanceby means of an aperture or apertures, 22, communicating with thecylinder forward of the piston, which is provided with an outletaperture, 23, communicating with the source of lower pressure.

The valve, 14, is normally held seated by yielding means, as a spring,15, (or springs) interposed between the inner face of the valve and apart connected with the piston, and therefore connected 4with the partto be actuated through the hollow piston rod, 5,

j or other higher pressure fluid, and provided in thisv instance with adust cap, 9. Obviously the inlet aperture, 8, could be connected with asource of pressure higher than atmospheric, if desired.

Auxiliary resistance means, as a spring, 25, interposed between the twovalves, and located within the chamber, 17, serves to normally hold thevalve, 16, in open position, as indicated in Figs. 2 and 3, and also totransmit to the larger valve, 14, the fluid pressure on the outer faceof the valve, 16,

and the pressure exerted by the operator toclose the valve, 16, thespring, 15, is suiiciently strong so that the valve,'16, may always beseated before the valve, 14, opens. The stem, 20a, of the valve, 16,extends through a sealing'member, 18, in the piston, 3, and is connectedto a valve actuating part, 20, extending through a sealing member, 2",in the cylinderA head, 2, and provided with means for connecting it withan operator operated part,

, It will be seen that the higher pressure,

valve, 14, is at all times subjected on its outer face to the higherpressure iluid, and that the lower pressure valve, 16, is likewisesubjected at all times to the higher fluid pressure, which istransmitted to the valve, 14, through the spring, 25, interposed betweensaid valves.

The inner surface or face of the higher pressure valve, 14is subjectedto the pressure in the portion, 11a, of the valve casing or chamber, 11,which is in constant communication with the `|cylinder in rear of thepiston, and when the lower pressure, or suction valve, 16, is o ned, theinner face of said valve will be subjected to the lower fluid pressure,and the higher pressure valve, 14, will also be subjected to the lowerfluid pressure at such time,

as the chamber, 17, within the valve, 14, communicates with the portion,11, of the valve casing, 11, through an aperture, 27, within the valveseat, 19, which is controlled by the valve, 16. When the valve, 16, isseated the marginal portions of its inner face, exterior lto the valveseat, will still be subjected to the lower Huid pressure,.which acts atall times upon these'mar 'nal portions. The area of the rear face o thevalve, 16, and the calibration of its auxiliary resistance spring, 25,are so related that said spring will hold the valve, 16, in openposition away from its seat A against the maximum dil'erential ofpressures on the opposite faces of the valve, 16, operating in adirection to seat the valve, 16. The diameter of the valve, 14, and thecalibration of the spring, 15, are so related that the the valve, 14.The stop for the open position of valve, 16, is its engagement with thepiston part, 10, at which time the pressure of spring, 25, isneutralized by itsv courriel?- tion on both sides with the piston.spring, 15, has suiiicient power to offer material resistance to themovement of the operator operated part in a direction to move the valve,15, away from its seat, whenthe .differential of fluid pressures on the'inner face of the valve, 14, and the outer faces'iof the valves, 14 and16, is at maximum, or inother words, said pressures are substantiallyequalized. It will also'be seen that the seat, 12, for the valve, 14,lforms a stop to limit its closing movement to which the pressure of thespring, 15, is transferred whenever the valve, 14, is closed.

In Fig. 1 the power actuator is shown diagrammatically installed in anautomotive vehicle in connection with Yan internal lcombustion enginefor propelling the vehicle, and arranged to operate the brake mechanismof the vehicle. In this ligure, the engine is4 represented at 60,provided with the usual carburetor, 62, and suction passage, 61,including the intake manifold, 63, the suction passage being providedwith the usual throttle valve, 64. The power actuator cylinder ismounted on the chassis of the Yvehicle and the outlet aperture, 23, fromthe cylinder forwardv of the piston is connected by suction pipe, 26,with the suction passage of the engine between the throttle valve andthe engine cylinders, and preferably with the intake manifold, 63, asshown, the suction pipe being preferably provided with a check valve,65, opening in a direction toward the man ifold. The piston rod, 5, ofthe actuator 1s connected with the part to be actuated, in this instancebrake mechanism of the vehicle, indicated diagrammatically in Fig.- 1.The brake mechanism may be of any preferred type, operating inconnection with two or more wheels 0I the vehicle. In Fig. 1 it isdiagrammaticall as a brake drum, 70, provided with a bra e'band, 71,brake operating lever, 72, and retracting spring, 73. The lever, 72, isconnected by link, 74, with the piston rod, 5, of the actuator. Theoperator operated part is in this instance afoot lever, or pedalv lever,81, provided, if desired, with the usual retracting spring, 82, tocounterbalance the weight and friction of the operator operated part,and is connected by link, 80, with the valve actuating part, 20.

When the parts are in normal or released position, as indicated in Figs.2 and 3, and the engine is running, the suction of the manifold willexhaust air from the cylinder on both sides of the piston and maintainthe piston ina state of rarecation, the air in the cylinder forward ofthe piston being withdrawn directly therefrom and the air in rear of thepiston being withdrawn through the ports, '13, in the piston hub, 10,the portion, 11a, of the 'valve casing, or chamber, 11, forward of thevalve, 14, the passage, 27, chamber, 17, of the valve, 14, passage, 21,in the valve, 16, the hollow valve stem, 20, and apertures, 22, therein,into the cylinder forward of the piston, from whence it is withdrawn tothe suction pipe, 26. In this position of the valve mechanism it will beseen that thevalve, 14, is exposed on its inner face to suction, 'andupon its outer face to the higher pressure fluid, in this case theatmosphere, and also to the atmospheric pressure on the outer face ofthe suction valve, 16`

thus providing the maximum differential of fluid pressures on the valve,1A, exerted in a direction to open the valve and overcome by thepressure of the spring, 15, which holds it closed. jThe suction valve,16, is also held open by the spring,`25, against the maximumdifferential of fluid pressures thereon. The spring, 25, is also nearlycoun-erbalanced by the maximum differential of fluid pressures on thevalve, 16, so that a very light initial pressure is required upon thefoot Vpedal to move the valve, 16, against the pressure of spring, 25,into closed position, which brings the va ve actuating part intooperative connection with the valve, 14) and move the valve, 14, in adirection away from its seat, or in other words, to open it. As soon,however, as the valve, 14, opens the higher pressure fluid `will passlinto the portion, 11, of the chamber, 11, and into the .cylinder inrear of the piston, and build up pressures in reary of the piston, andin the portion, 11a, of chamber, 11, ythereby gradually reducing thedifferential fluid' pressures, to which said valve is subjected andgraduallytransferring the retracting.l force 'for' resistance of thespring, 15, to thefopera'tor operated part, in

a direction to-resist the forward movement thereof. The chamber, 12',lis connected at i all times yw'ithvthe suction source, even when thevalve, 16, is'fseatedand valve, 14, is open. Therefore the areas ofbothvalves represented by the annular chamber, 17, are neutralized so far asthe suction is concerned and the rear face of the suction valve becomesvirtually a portion of the rear pressure face of the atmospheric valve,and as the suction valve is seated and there is an equalization of fluidpressures on opposite sides of the valves, the resistance of the suctionspring, 25, is

added to the operator' operated part. Therefore, the operator meetsgradually increasing resistance of the main resistance means for thehigher pressure valve, and the resistance means for the lower pressurevalve, as the pressure builds up in the cylinders, and moves the pistonforward to apply the brake mechanism, and the greater the force exertedlupon the braking surfaces, the greater the pressure built up in thecylinder in rear of the piston to effect that braking, and the greaterthe force which must be exerted by the operators foot on the pedal tokeep the suction valve closed and the air inlet valve open to attainthat pressure.

It is also to be noted that all the force exerted by the driver inovercoming the resistance of the springs, 15 and 25, is exerted in thedirection of movement of the piston in effecting its power stroke andwill be transmitted to the piston therefor and to the brake mechanism(or other part to be operated) in,

the direction of the power stroke of the piston, so that this forcewhich is required to overcome these springs is not lost, but isconserved and applied to the part to be operated. v

As soon as the forward movement of the operators foot and the pedal,ceases, thel piston will overtake the valve actuating part, 20,permitting the higher pressure valve, 14, to close without opening thesuction valve, 16, and thus holding the brakes applied. As soon as thevalve, 14, closes, the pressure of the resistance spring, 15, will betransferred from the operator operated part to the valve seat, 12, andthe operators foot is' relieved from the pressure of this spring, andhas only to overcome the resistance of the spring, 25. The operator isthus relieved of the greater portion of the pedal pressure in holdingthe brakes applied for a considerable length of time, as in prolonged orcontinued braking. If the operator wishes to effect a further pressureon the braking surfaces, however, it will benecessary for him to exertsufficient pressure to overcome the increased resistance of the spring,15, and reopen the valve, 14. The pressure of the resistance spring willbecome maximum when the pressure in the cylinder in rear ofthe piston isequal to the higher fluid pressure, in this case atmospheric pressure.

It will also be seen that as all physical force of the operator isapplied to the piston in the direction of its power stroke, that afterthe brake mechanism has been applied to the full capacity of the poweractuator, the operator may, by exerting further pressure on the pedal,bring the valve, 14, into engagement with the portion of the piston, 3,and apply his physical force in addition t0 that of the actuator, and inlike manner may apply the brakes by physical force alone in case offailure of power, in which case thel first portion of the movement willoperate the valve mechanism as before described, and vent the cylinder.

To release the brakes it is only necessary for the operator to releasethe pedal lever, 81, sufciently to permit the suction valve to be openedby the spring, 25. This will el'ect analmost immediate equalization -ofpressures wit-hin the cylinder, in the form of actuator herein shown, bytransfer from the high pressure side to the low pressure side,permittingan immediate release of the brake' mechanism under the actionof its retracting ,means and connecting both ends of the cylinder withthe suction passage of the engine and withdrawing the air previouslyadmitted to apply the brakes, the piston, and brake mechanism, beingreturned to their normal or released position, or retracted positions bythe retracting means, as the spring, 73.

It will be seen that byour invention the operator is enabled todetermine very accurately the amount of power which is being applied tothe brake mechanism by the actuator,

by the variations in the resistance to the operator operated part foractuating the valve mechanism in, substantially the same manner as whenoperating ordinary hand or foot operating brake mechanism, while thebrakes are actually applied by the power of the actuator, and as beforestated, the operator is relieved from this increased resistance, that isto say, that of the spring, 15, by the seating I' of the valve, 14, tohold the brakes applied.

By reason of the fact that the force exerted by the operator inoperating the valve mechanism in opposition to the springs, 15 and 25,is conserved and applied to the piston in the direction of its powerstroke, a cylinder of smaller size and less weight may be employed to dothe same work as a larger and heavier one with economy of manufactureand convenience in the installation, and correspondingly smaller4quantities of air lwill be withdrawn into the suction passage of theengine with each application of the brake mecha.

nism with less liability of interfering with the operation of theengine, or stalling it if idling.

In the preceding figures we have illustrated an embodiment of ourinvention in a power actuator, the piston of which is submerged invacuum when in the retracted position, the valve mechanism beinginstalledA m a valve casing which is a part of the piston hub. It willbe obvious, however, that the valve mechanism for the actuator may belocated in a valve casing exterior to the piston and cylinder of theactuator and connected, for example, in the linkage between the operatoroperated part and the brake mechanism or other part to `be'operatedthevalve casing moving with the piston and being connected with thecylinder to the rear of the piston and with the suction passage byflexible connections extending from suit-l able ports corresponding to asingle port, 13 and port, 23, of the cylinder, in a manner similar tothat illustrated in our former application for Letters Patent of theUnited States filed June 17, 1927, and given Serial No. 199,477.

It will be obvious that more than one cylinder could be controlled bythe valve mechanism by suitable pipe connections between the corresonding parts of the several cylinders. or example, we have shown in Fig.2, the cylinder, 1, provided at its opposite ends with pipes, 30 and 31,for connecting it with the corresponding portionsof one or a pluralityof valveless cylinders having pistons therein, so that the pistons ofall the connected cylinders will be operated simultaneously under thecontrol of the single valve mechanism. The pipes, 30 and 31, are shownprovided with cut o cocks, 30a and 31a, so that the said pipes maybeclosed when not in use.

It is also obvious that our invention is applicable in connection withany type of power actuator which comprises relatively movable coactingmembers, at least one of which is connected with the part to be operatedand with the casing of the valve mechanism.

Whatwe claim and desire to secure by Letters Patent is 1. Valvemechanism for controlling the operation of fluid pressure actuatorsc'omprising among its members a valve casing, provided with a valve seatwithin the same, and a higher fluid pressure inlet communieating with aportion of the casing on one side of said seat, and a passagecommunicating with a portion of said actuators and the casing on theother side of said seat, a higher pressure valve and a lower pressurevalve of diierent sizes in said casing, said higher pressure valve beingthe larger and normally engaging said seat and having opposite faces ofunequal e'ective pressure areas, a portion of one of said faces beingalways exposed to the higher fluid pressure, said valve face beingprovided with an aperture, a recess and a valve seat, and the lowerpressure valve being movable within said recess with respect to thehigher pressure valve into and out of engagement with said seat andhaving its outer face subjected at all times to the higher fluidpressure, sealing means between the low pressure valve and said recess,a hollow valve stem for said lower pressure valve passing through saidaperture and provided with an aperture communicating with said recess,and an aperture communicating with a source of lower Huid pressure, theother face of said higher pressure valve being exposed to the lower Huidpressure when said valve is seated, and the lower pressure valve isopen, yielding resistance means on the oppoi site face of the higherpressure valve from said recess for normally seating said valve againstthe maximum differential of fluid pressures thereon, said resistancemeans being capable of offering material resistance to the movement ofsaid valve in a direction away from its seat when the fluid pressures onopposite faces of said valve are equalized, and being nearlycounterbalanced by the maximum differential of Huid pressures thereonand being interposed between said valve and a part connected with thevalve casing, said valve stem being provided with means for connectingit with an operator operated part, the movement of said operatoroperated part in a direction to seat said lower pressure valve eecting aconnection between said valve and said higher pressure valve in adirection to open the higher pressure valve.

2. In a power actuator, the combination `of a cylinder closed at bothends, a piston therein, providedwith meansl for connecting it with apart to be operated, controlling valve mechanism, and means forconnecting the cylinder with sources of higher and lower fluid pressuresunder the control of said valve vmechanism, said valve mechanismcomprising among its members a valve casing operatively connected withand movable with the piston and provided with a valve seat within thecasing and an aperture on each side of said seat, one communicating withthe higher fluid pressure source and the other communicating with aportion of said cylinder, a higher pressure valve and a lower' ingresistance means for normally seating said valve against-the maximumdifferential of fluid pressures, thereon, said 'resistance means beingcapable of ofering material resistance to the movement of said valve ina direction away from its seat, when the fluid pressures on said valveare equalized and be- .ing nearly counterbalanced by the maximumdifferential of fluid pressures thereon, and

being interposed between said valve and a,

part connected with thevvalve casing, said valve lbeing provided on theface opposite that engaged by said resistance means with a recessprovided with an aperture and a valve seat, the lower pressure valvebeing movable into and out of engagement with 'said seat and having itsouter face subjected at' all times to the higher liuid pressure, andprovided with sealing means preventing the passage of higher Huidpressure into said recess when the higher pressure valve is closed, andhaving its inner face subjected to the pressure within said recess,auxiliary yielding resistance means interposed between said valves andhaving suicient power to hold said second mentioned valve unseatedagainst the maximum di'erential of fluid pressures on the opposite facesof said valve, a hollow valve stem for said second mentioned valveprovided with an aperture within the valve casing communicating withsaid recess, and an aperture exterior tov said valve casingcommunicating with said source of lower pressure, an operator operatedpart connected with said valve stem,.the movement of said operatoroperated part to close said lower pressure valve effecting the conf,

nection of the operator operated part with said higher pressure valve,to permit the opening of the latter, to effect a power stroke of theactuator piston, the initial resistance of said main and auxiliaryresistance-means to the said movements of saidvalves being increasedsubstantially in proportion to the variation in the differential of luidpressures on said valves, to enable the operator to determine the amountof pressure applied to the actuator piston and the part connectedtherewith.

3. In a power actuator, the combination of a cylinder closed at bothends, a piston therein, provided with means for connecting it with apart to be operated, controlling valve mechanism, and means forconnecting the cylinder with sources of higher and lower fluid pressuresunder the control of said valve mechanism, said valvemechanismcomprising among its members a valve casing operativelyconnected with and movable with the piston and provided with a valveseat with- -in the casing and an aperture on each side of'said seat, onecommunicating with the higher fluid pressure source and the otherIcommunicating with a portion of said cylinder, a higher pressure valveand a-lower pressure valve in said casing movable with and with respectthereto and with respect to each other, the higher pressure valve beinglarger 'than the lower pressure valve and normally engaging said seatand having opposite faces of unequal effective pressure areas, one ofsaid faces being exposed to the higher iuid pressure, and the other facebeing exposed `to the lower fluid ressure when the valve is yseated `andthe va ve mechanism is in ormal or released position, yieldingresistance means for normally seating said. valve against the maximumdierential of Huid pressure thereon, said resistance means being capableof offering material resistance to the movement of said valve, .in adirection away from its seat, when the fluid pressures on said valve areequalized and being nearly counterbalanced by the maximum difieren- Ciltial of fiuid pressures thereon, and being interposed between said valveand a part connected with the valve casing, said valve being provided onthe face opposite that engaged by said resistance means with a recessand an aperture extending through the valve and provided with a valveseat, the lower pressure valve being movable into and out of'engagementwith said seat and having its outer face subjected at all times to thehigher Huid pressure and provided with sealing means preventing thepassage of higher fluid pressure into said recess when the higherpressure valve is closed, and having its inner face subjected to thepressure within said recess, auxiliary yielding resistance meansinterposed between said valves and having sufficient power to hold saidsecond mentioned valve unseated against the maximum differential offluid pressure on the opposite faces thereof, a hollow valve stem forsaid second mentioned valve provided with an aperture'within the valvecasing communicating with said recess, and an aperture exterior to saidvalve casing communicating with the source of lower .fiuid pressure, anoperator operated part connected with said valve stem, the movement ofsaid operator operated part to close said lower pressure valve effectingthe connection of the operator operated part with said higher pressurevalve, to permit the opening of the same, to effect a power stroke ofthe actuator piston, andthe direction of said movement of the operatoroperated part and valves being in the same direction as the power strokeof the piston, the initial resistance of said main and auxiliaryAresistance springs to said movement of the operator operated part beingincreased substantially in proportion to the variation inthedifferential of fluid pressures on said valve, to enable the operator todetermine the amount of pressure applied to the actuator piston and thepart connected therewith and the force exerted by the operator toovercome said resistance being conserved and transmitted to the part tobe operated.

4. In aj power actuator, the combination of a cylinder closed at bothends, apiston therein, provided with means for connecting it with a partto be operated, controllingV valve mechanism, and means for connectingthe cylinder with sources of higher andlower Vfluid pressures under thecontrol of said valve mechanism, said valve mechanism comprising amongits members a valve casing operatively connected with and movable withthe piston and provided with a valve seat within the casing and anaperture oneach side of said seat, one communicating with the higherpressure source, and the other communicating with a portion of saidcylinder, a higher pressure valve and a lower pressure valve ofdifferent sizes in saidcasing movable withand with respect thereto andwith respect to each other, the higher pressure being larger than thelower pressure valve, and normally engaging said seat and havingopposite faces of unequal effective pressure areas, a portion of one ofsaid faces being always exposed to the higher fluid pressure, said valveface being provided with a recess, an aperture extending through thevalve, and a valve seat therefor, and the other of said faces beingexposed to the lower fluid pressure when the valve is seated and thevalve mechanism is in normal or released position, yielding resistancemeans for normally seating said higher pressure valve against themaximum differential of fiuid pressures thereon, said resistu ance meansbeing capable of offering material resistance to the movement of saidvalve, in a direction away from' its seat, when the fluid pressures onsaid valve are equalized and being nearly counterbalanced by the maximumdifferential of fluid pressures thereon, and being interposed betweensaid valve and a part connected with4 the valve casing, the lowerpressure valve having a 'portion to engage said seat and a portionhaving a sealing engagement with the wall of said recess and having itsouter face subjected at all times to the higher pressure fluid,auxiliary yielding resistance means interposed between said valves andhaving suflicient power to hold said lower pressure valve unseatedagainst the maximum differential of fluid pressures on said valve, saidlower pressure valve being provided with a hollow valve stem having anaperture within the valve casing communicating with said recess and anaperture exterior to said valve casing communicating with the source oflower fluid, and an operator operated part connected with said valvestem, the movement of said operator operatedl partito seat the lowerpressure valve effecting the connection of the operator operated partwith the higher pressure valve to permit the opening ofthe same toeffect a power stroke of the actuator piston, the initial resistance ofsaid main and auxiliary resistance means to said movement of saidvalves, being increased substantially in proportion to the variation inthe differential of fluid pressures on said valves to enable theoperator to determine the amount of pressure applied to the -actuatorpiston and the part connected therewith, and means for limiting therelative movement of said valve stem with respect to the valve casing toenable the operator to apply his physical force to the part to beoperated in addition to any power exerted by the actuator and in 'caseof failure of power, to vent the cylinder and apply the brakes byphysical force alone.

5. In a power actuator, the combination of a cylinder closed at bothends, a piston therein, provided with means for connecting it with apart to be operated, controlling valve mechanism for the actuator,comprising a valve casing, connected with the piston and movabletherewith and being provided with a valve seat within the same, anaperture on one side of said seat communicating with the cylinder on oneside of the piston, and an aperture on the other side ofvsaid seatcommunicating with the source of higher fluid pressure, a higherpressure valve engaging said seat and having an inner face exposed atall times to the pressure within the portion of the cylinder in rear ofthe piston, and a portion of the exterior face uof said valve beingexposed at all times to the higher fiuid pressure, said exterior facebeing provided with a recess, a passage for connecting said recess withthe valve casing on the opposite face of said valve, and with saidportion of the cylinder, and a valve seat surrounding said passage,yielding resistance means interposed between the inner face of lsaidvalve and the piston, normallyl holding said valve closed against thepressure of the higher pressure fluid, and having suflicient power tooffer material resistance to the movement of said valve inaavdirectionaway from its seat, when the fluid pressures on opposite faces of saidvalve are equalized, vand being nearly counterbalanced byv the maximumdifferential of fluid pressures on the opposite faces of said valve,means for connecting the cylinder forward of the piston with the sourceof lower pressure, a lower pressure valve provided with a portion forengagingk the valve seat in said recess and a portion having a sealingengagement with the wall of said recess, a hollow valve stem for saidvalve, provided with a passage for connecting said, recess with t-helportion of said cylinder forward of the piston, whereby7 the iston isnormally maintained submerged in t e lower fluid pressure when the valvemechanism is in the normal or released position, auxiliary resistance.means interposed between said valves and having sufficient strength tohold the lower. pressure valve away from its seat against the maximumdifferential of fiuid presures on said valve, and an operator operatedpart'connected with -said lower pressure valve, the movement of saidoperator operated part to seat the lower pressure valve effecting aconnection of the operator operated part with the higher ressure valve,to permit the opening o the latter, the initial resistance oflsaidresistance means to the movement of the operator o'perated part to closethe lower pressure valve and open the higher pressure valve to effect apower stroke of the piston, being increased by the variations in thedifferential of fiuid pressures on the opposite faces of said valves.

6. In brake mechanism for an automotive vehicle provided with aninternal combustion engine having a carburetora suction passage'therefrom to the engine cylinders, and a throttle valve for saidpassage, the combination of a power actuator comprising a cylinderclosed at both ends, a piston therein, operatively connected with brakemechanism of the vehicle, controlling valve mechanism, means forconnecting the cylinder on one side 0f the' piston with the suctionpassage of the engine between the throttle valve and the enginecylinders, and for connecting the cylinder on the other side of thepiston with the suction passage of the engine and with a source ofhigher fluid pressure under the control of said valve mechanism, saidvalve mechanism comprising a valve casing connected with the piston andprovided with a valve seat within the same, and an aperture on one sideof said seat, communicating with ,said last mentioned portion of thecylinder,

and another aperture on the opposite side of said seat communicatingwith the source of higher pressure, a higher pressure valve, and asuction valve in said casing, the higher pressure valve normallyengaging said seat and' having opposite faces of unequal effecltivepressure areas exposed respectively to the higher fluid pressure and thesuction of said suction passage when the valve is seated and the valvemechanism is in normal position, yielding resistance means normallyseating said `valve against the maximum differential of fluid pressuresthereon, said resistance means being capable of offering materialresistance to the movement of said valve in a direction away from itsseat when the fluid pressures on opposite faces. of said valve areequalized and being nearly counterbalanced by the maximum differentialof fluid pressures thereon, and being interposed between said valve andthe part connected with the valve casing, said valve being provided withan aperture therethrough, and provided on the face opposite that engagedby said yielding resistance means with a valve seat for said aperture,the suction valve beingr movable into and out of engagement with saidseat and having its outer face subjected at all times to the higherfluid pressure, a recess being formed between said valves, sealing meansbetween said recess and the suction valve, a hollow valve stem for saidji;

suction valve, provided with an aperture communicating with said recessbetween said valves, and an aperture communicating with said portion ofcylinder connected with the suction passage, auxiliary yieldingresistance means interposed between said valves and having suficientpower to hold said suction valve unseated against the maximumdifferential of fiuid pressures on the opposite -faces of said valve,and an operator op- L" erated part, connected with said valve stem, themovement of said operator operated part in a direction to seat saidsuction valve, effecting a connection between the operator operated partand the higher pressure valve to permit the opening of the latter afterthe suction valve has seated, to effect the power stroke of the piston,the initial resistance of said resistance means increasing by variationsin the dilerential of fluid pressures'on said valves in substantialproportion to the power exerted upon said piston and the brakemechanismconnected therewith. l

7. In brake mechanism for an automotive vehicle provided with aninternal combustion 'engine having a carburetor, a suction passageleading to the engine cylinders, and a throttle valve for said passage,the combination of a power actuator comprising a cylinder closed at bothends, a piston therein operatively connected with brake mechanism of thevehicle, controlling valve mechanism for the actuator, means forconnecting the cylinder forward of the piston with the suctionl passageof the engine between the throttle valve and the engine cylinders, andfor connecting the cylinder in rea-r of the piston with the suctionpassage of the engine and with a source of higher fluid pressure underthe control of said valve mechanism, said controlling valve mechanismcomprising a valve casing connected with the piston and provided with avalve seat within the casing, an aperture on one side of said seat,communicating with the cylinder in rear ofthe piston, and an aperture onthe other side of said seat, communicating with the source of higherpressure, a higher pressure valve for engaging said seat, having itsinner face exposed to the pressure within the portion of the cylinder inrear of the piston, and its outer face exposed to the pressure of thehigher pressure iiuid, yielding resistance means normally seating saidvalve against the higher fluid pressure, interposed between said valveand the part connected with the piston and having sulicientpower tooffer material resistance tothe movement ofsaidvalve in a direction awayfrom its seat when the fluid pressures on opposite faces of the valveare equalized, and beingV nearly counterbalance'd by the maximumdifferential of fluid pressures thereon, said valve having its outerface provided with a' recess, a passage for connecting said recess withthe portion of the valve casing onthe opposite face of the valve, and avalve seat in said recess surrounding said passage, a suction valve insaid recess having a portion for engaging said valve seat and having itsouter face exposed' to higher fluid pressure within said casing,auxiliary yielding resistance means interposed between said valves andhaving suilicient power to maintain the suction valve in open positionagainst the maximum differential of Huid pressures on said valve," meansfor connecting said recess with vthe suction passage of the engine, andan operator operated part connected with the suction valve, the movementofsaid'operator operated part andhavin to close the suction valve,elfecting a connection between the operator operated part and the higherpressure valve to permit to be opened to effect the power stroke of thepiston, the initial resistance of said resistance means being increasedin opposition to said movement of the operator operated part by thevariation in differential of fluid pressures on opposite faces of saidvalves in substantial proportion tothe power exerted upon the piston andthe brake mechanism connected therewith. l

8. In brake mechanism for an automotive vehicle provided with aninternal combustion engine having a carburetor, a suction passageleading to the engine cylinders, and a throttle valve for said passage,the combination of a power actuator comprising a cylinder closed at bothends, a piston in said cylinder operatively connected with brakemechanism of the vehicle, controlling valve mechanism for the actuator,means for connecting the cylinder forward of the piston with the suctionpas-- sage, between the throttle valve and the engine cylinders,'and forconnecting the cylinder 1n rearof the piston with the suctionV .passageand with a source of higher fluid pressure under the control of the saidvalve mechanism, said valve mechanismI comprising a valvecasingrconnected and movable with the piston, andy provided with a valveseat, an aperture on one side of the valve seat connected with thecylinder in rear of the piston, and an aperture on the other side of thevalve seat connected with the source of higher fluid pressure, a higherpressure valve in said casing normally engaging said seat its inner faceexposedto pressure within sai portion of the cylinder in rear `of thepiston and its exterior face exposed to the higher liuid pressure,.yielding .resistance means interposed between said valve .and a partconnected with the piston and normally ble of offering materialresistance to the movement of said valve in a direction away'from itssea-t when the -fluid pressures on opposite faces of said valve areequalized, and being nearly counterbalanced by the maximum differentialof fluid pressures thereon, said valve being provided on its outer facewith a recess,

a passa-ge connecting the recess with the valve casing on the oppositeface of the valve, and a valve seat surrounding said passage, a suctionvalve in said recess having a portion to engage said seat, and a portionhaving a sealing engagement with the wall of the recess, auxiliaryyielding resistance means interposed between said valves and havingsuf-v ficient power to hold the suction valve unseated against themaximum differential of fluid pressures on its opposite faces, thesuction valve having its outer face exposed at all times to the higherfluid pressure and portions of its inner face exposed at all times tosuction, said suction valve being provided with a passage connectingsaid recess with the cylinder on the forward side of the piston, wherebythe piston will normally be maintained submerged in vacuum whenthepiston and valve mechanism are in released positions, and the powerstroke of the piston may be eifected without .admitting any appreciableamount of higher pressure fluid to the suci tion passage and anvoperator operated part l connected wlth said suction valve, themovement of the suction .valve into closed position of fluid pressureson opposite faces of said valves in substantial proportion to the pres-.sure exerted upon the piston and brake mechanism.

9. In brake mechanism for an automotive vehicle provided with aninternal combustion engine having a carburetor, a suction passageleading to the engine cylinders, and a throttle valve for said passage,the-com bination of a power actuator comprising a cylinder closed atboth ends, a piston in said vcylinder operatively connected with brakemechanism of the vehicle, controlling valve mechanism for the actuator,means for connecting vthe cylinder forward of the piston with thesuction passage, between the throttle valv'e and the engine cylinders,and for I connecting the cylinder in rear of the piston with the suctionpassage and with a source of higher fluid pressure under the control ofthe said valve mechanism, said valve'l mechanism comprising a valvecasing connected and movable with the piston, and provided With`a valveseat, an aperture on one side of the valve seat connected with thecylinder in rearfof the piston, and an aperture on the other side of thevalve seat connected with the'source o f higher fluid pressure, a higherpressure valve in said casing normally enand having its inner face ex-@posed to pressure within said portion of the cylinder in rear of thepiston and its exterior face 'exposed to the higher fluid pressure,

l yielding resistance means interposed between said valve and apartconnected with the-piston and normally 'seating said' valve againstthe higher uid pressure, said resistance means being capable of oieringmaterial resistance to the movement of said valve in a 'direction awayfrom its seat when the iuid'l; .pressures on-opposite faces lofsaidvalve are equalized, and being nearly counterbalanced bythe maximumdiierential of fluid pressures thereon, saldvalve being provided on itsouter face with a recess, a passage ,connecting the recess with thevalve casin on the opposite face of the valve'and a va ve seatsurrounding said passage, a suction valve in said recess having aportion to engage said seat, and a portion having a sealingyengagementwith the wall of the 'recesstauxiiiary yielding `resistance meansinterposed between said valves and having suilicient power to hold thesuctionvalve unseated against the maximum dierential of fluid pressureson its opposite faces, the suction valve having its outer face exposedat all times to the higher fluid pressure and portions of its inner faceexposed at all times to suction, said suctio valve being provided with apassage connec ing said recess with thecylinder on the forward side ofthe piston, whereby the piston will normally be maintained submerged invacuum when the piston and valve mechanism are in released positions,and the power stroke of the piston may be ei'ected without admitting anyappreciable amount of higher pressure fluid to the suction passage, andan operator operated part connected with said suction valve, themovement of the suction valve into closed position effecting aconnection between the operator operated part and the higher pressurevalve to permit the opening thereor` to effect the power strokev of thepiston, the

linitial resistance to the movement of the \op-.

erator operated part to c'lose the suction valve and open the higherpressure valve being gradually increased by the variations in thedifferential of fluid pressures on` opposite faces of said valves insubstantial proportion to the pressure' exerted upon the piston andbrake mechanism, and meansI for limiting the movement of the operator,operated part with respectto the piston, to enable the operatcr to applyhis physical force to the brake mechanism in addition tothat exerted bythe actuator and to operate the valve mechanism to vent the cylinder andapply the brakes by his physical force .in case of failure of power.

10. In brake mechanism for automotive vehicles provided with an internalcombustion engine having a carburetor, a suction passage therefrom tothe engine cylinders, and a throttle valve for said passage, thecombination of a power actuator comprising a cylinder closed at bothends, a piston in saidcylinder provided with means for connecting itwith brake mechanism of the vehicle and controlling valve mechanism,means for connectingv the cylinder forward of the pistonY with thesuction passage and for' connectin the cylinder in rear' of the pistonwith te suction passage and with a source of higher pressure under thecontrol of said valve mechanism, said valve mechanisin comprisingaavalve casing connected to and movable with the piston, and provided witha valve seat, said casing being connectedforward of said seat with theportion of the lcylinder in rear of the piston, and connected in rear ofsaid seat at all times with the higher pressure fluid source, said valvehaving on its rear face arecess, open at its rear end, and having apassage through the valve, for placing said recess in communica-vportions in sealing engagement with the higher pressure valve, the rearface of the suction valve, and the portions of the rear` face of thehigher pressure valve exterior to the suction valve being subjected atall times to the higher fluid pressure, means for connecting theinterior of said recess, betweensaid valves at all times with theportion of the cylinder forward of the piston, and thereby connecting itwith the suction passage, the passage through the higher pressure valveserving to connect the cylinder in rear of the piston with the suctionpassage when the suction valve is open, to maintain the plston submergedin vacuum when the pist'on and valves are in normal or releasedpositlon, a main spring, resistance means interposed between the higherpressure valve and apart connected with the casing, and acting on thevalve in a direction to seat it, an auxillary resistance meansinterposed between said valves, and acting on the suction valve 1n adirection to unseat it, said main resistance means having sufficientpower to offer material resistance to the movement of the higherpressure valve in a direction away from its seat, when the fluidpressures on opposlte sides of said valves -are equalized and beingnearly count'erbalanced by the higher Afluid pressure'on the outerfacesof said valves, 'the pressure of said auxiliary resistance means beingnearly counterlbalancedby the differential of fluid pressure on opposltefaces of the suction valve, and an operator operated part connected withthe .suction valve, for moving it into-seating engagement with thehigher pressure valve and opening the latter to produce a power strokeof the piston, the light initial resistance of sald resistance means to`such movement of the operator operated part being increased 'by thevariations in the differential of fluid pressures on opposite faces ofsaid valves, inl substantial accordance with the power exerted by theactuator piston.

,11. In brake mechanism for automotive vehicles provided with aninternal combustion engine haviigv la carburetor, a suction passagetherefrom tothe engine cylinders, and a throttle valve for said passage,the combina- -tion of a power actuator comprising a cylfinder closed atboth ends, a piston in said cylinder provided with means for connectingit with brake mechanism of the vehicle and controlling valve mechanism,means for connecting the cylinder forward of the piston with the suctionpassage and for connecting the cylinder in rear of the piston with thesuction passage and with a source of higher pressure under the controlof said valve mechanism, said valve mechanism comprising a valve casingconnected to and movable with the piston, and provided with a valveseat, said casing being connected forward of said seat with the portionof the cylinder in rear of the piston, and connected in rear of saidseat at all times with the higher, pressure fluid source, said valvehaving on its rear face a recess, open at its rear end, and having apassage through the valve, for placing said recess in communication withthe portion of the casing forward of the valve, and being provided witha suction valve seat for said passage within said recess, a suctionvalve of smaller diameter than the higher pressure valve closing therear end of said recess, having portions to engage the suction valveseat and having portions in sealing engagement with the higher pressurevalve, the rear face of the suction valve, and the portions of the rearface of the higher pressure valve exterior to the suction valve beingsubjected at all times to the higher fluid pressure, means forconnecting the interior of said recess, between said valves at all timeswith the portion ofthe cylinder forward of the piston,l and therebyconnecting it with the suction passage, the passage through the higherpressure valve serving to connect the cylinder in rear of the pistonwith the suction passage when the suction valve is open, to maintain thepiston submerged in vacuum when the piston and valves are in normal orreleased position, a main spring, resistance means interposed betweenthe higher pressure valve and a part connected with the casing, andyacting on the valve in a direction to seat it, /an auxiliary resistancemeans interposed between said valves,'and acting on the suction valve ina direction to unseat it, said main resistance means having suiiicientpower to offer material resistance to the movement of the higherpressure valve 1n a direction away fromits seat, when the fluid lof thepiston, said connections permitting both valves to be simultaneouslyseated, the

-Lesa-11'? initial pressure of said resistance means behaving ingincreased by' variations inthe differential of fluid pressure onopposite faces of said valve, and the seating of the higher pressurevalve without opening the suction valve, transferring theresistance ofsaid main resistance7 means from the operator operated part to the valvecasing, while maintaining the predetermined differential offluidpressures on the iston and on said valves. v

12. -In bra e mechanism for automotive vehicles provided with `aninternal combustion engine having a carburetor, a suction '1'5 passagetherefrom to the engine cylinders,

and a throttle valve for said passage, the

combination of a power actuator comprising a cylinder closed at bothends, a piston in said cylinder provided with means for connecting itwith brake-'mechanism of the vehicle and controlling valve mechanism,means for connecting the k ylinderforward of the piston l 3g', seat,said casing being connected forward of with the suctlon passage and forconnecting the` cylinderin rear of the piston with the suction passageand with a source of higher pressure under vthe control of saidv valvemechanism, said valve mechanism comprising a valve casing connected toand movable .with the piston, and provided with'a valve said seat withthe portion of the cylinder in rear of the piston, and connected in rearof said seat at all times with the higher pressure v fluid source, saidvalve havingon its rear face a recess, open at its rear end, and havinga passage through the valve, for placing said recess in communicationwith the portion of the casing forward of the valve, and being providedwith a suction valve seat fornsaid passage within said recess, a suctionvalve of smaller diameter than the higher pressure valve closing therear end of said recess, having portions to engage the suction valveseat and having portions in sealing engagement with the higher pressurevalve, the rear face of the suction'valve, andthe portions' ofthe rear4face of the higher pressure valve exterior to the suction valve beingsubjected at all timesl to the higher ui'd pressure, means for vconnecting the interior .of said re'cess,'between 'said valves at alltimes with the portion of the cylinder .forward of the piston, andthereby connecting it with the suction passage, the

l passage through the higher pressure valve serving t o connect thecylinder in rearof the plston with" the suction passagev when thesuction valve open, to maintain the piston v submerged 'jin vacuum 4whenthe piston and valves are in' normal or released position, a mam spring,resistance means lnterposed between the luglierj pressure valve and apart connected with the casing, and acting on the valve ina direction toseatit, an auxiliary re- Isistance meansV interposed between saidvalves, and acting on the suction valve in a direction to unseat it,said main resistance means ,suilicient power to offer materialresistance to the movement of the higher pressure valve in a directionaway from its seat,whenthe fluidpressures on opposite sides of saidvalves are equalized, and being nearly counterbalanced by the higherfluid pressure lon the outer faces of said valves, the pressure of saidauxiliary resistance means being nearly counterbalanced by thediierential'of fluid pressure on opposite faces of thesuction valve, andan operator operated part connected with the suction valve, for movingit into seating engagement with the higher pressure valve andopening-the latter to produce a power stroke of the piston, saidconnections permitting both valves to be simultaneously seated, theinitial pressure of saidresistance means being increased by variationsin the differential of Huid pressure on opposite faces of said valve,and the seating of the higher pressure valve without opening the suctionvalve, transferring the resistance of saidrmain re- .sistance means fromthe operator operated part to the valve casing, while maintaining thepredetermined differential of iuid pressures on the piston and on saidvalves, and means for limiting the relative movement between the pistonand the' operator operated part to enable the operator to addhisphysical force to the brake mec-hanisnrI in addition to any powerexerted vby the actuator, and in case of failure of power to vent thecylinder andV` apply the brakes by his physical force.

13. Valve mechanism for controlling the*Y operation of fluid pressureactuators comprising a casing, high and low pressure valves movablymounted thereinand arranged to control differentials of fluid pressureto said actuator, means for connecting said casing I with sources ofhigher and lower fluid pressure, said valves being normally subjected tothe maximum differentialof Huid pressures, f and resistance elementsslightly overbalancing the differentials on said valves when saiddifferential-is at maximum together with an operatory operated part for,operating said valves'l against said` resistance elements.

14. Valve mechanism for controlling the J sure on the high pressurevalve, an auxi iary resistance element arranged .to slightly overbalancethe differentials of pressure on the low pressure valve, and an operatoroperated part for operating said valves to control differentials of Huidpressure to the actuator.

15. Valve mechanism for controlling the operation of fluid pressureactuatorscomprising a valve casing, high and low pressurea valves movablmounted therein, means for onnegting sai casing with sources of higherand lower pressure, said valve being subjected when in normal positionto maximum 'differentials of fluid pressure, a resistance elementslightly overbalancing the dillerential of pressure on the high pressurevalve, an auxiliary resistance element slightly overhalancing thedifferential of pressure on the low pressure valve, and an Qperatoroperated part connected to` the low pressure valve, and arranged tosequentially overcome the auxiliary resistance element and theresistance element of the high pressure valve to control diffe-rentialsof fluid pressure vto the actuator to produce a power stroke thereof.

16. Valve mechanism for controlling the operation of fluid pressureactuators comprising a valve casing, high and low pressure valvesarranged therein, means for connecting said casing with higher and lowerfluid sistance element to controldilerentials of fluid-pressure to theactuator, said resistance,V

tures. j

I CALEB S. BRAGG.

VICTOR W.` KLIESRATH.

pressures, said valves being subjected when f in normal position tomaximum differentials of fluid pressure, a mainresistance elementinterposed between the high pressure valve and the casing and slightlyoverbalancin maximum dierentials of pressure on sai high pressure valve,an auxiliary resistance element arranged between the high pressure A,valve and the low pressure valve and slightly overbalancing thedifferentials of pressure on said low pressure valve, la stop on saidhigh pressure valve and an operator operated part connected with the lowpressure valve and arranged to bring the same into engagement withtbestop on the high pressure valve to sequentially overcome the auxiliaryelement andthe main resistance element to control differentials ofpressure to the actuator.I

17.. Valve mechanism for controlling the operation lof fluid pressureactuatorscomprising a valve casing, a high pressure valve movablymounted therein and provided with ,a -recess having a seat, a lowpressurey valve slidably mounted in the recess and arranged to engagesaid seat, means for connecting 'the casing with differentials of fluidpressure, 5g saidfvalves being subjected to maximum difv erentials offluid pressure when in normal retracted position, a main resistanceelement inter osed between the high pressure valve and t e casing andarranged to slightly overr Ico balance the differentials of fluidpressure on said high pressure valve, an auxiliary resist-I y anceelement arranged in said recess between the high (pressure valve and thelow pressure 1 valve an adapted to slightly overcometthe differentialsof pressure on said low pressure valve, and an operator loperated partcone nectedwith said low pressure valve and arranged to bring the sameintoengagement with said Vseat to sequentially overcome the 65.auxiliary resistance element and the main re-l

